Compressed air is a valuable energy source. When air is compressed, the moisture content of the air is released as water vapor which forms condensate. Condensate is an unwanted byproduct of air compression. Condensate occupies a portion of the volume of an air compression chamber thereby decreasing the working volume of the chamber. The more space the condensate occupies in the air compression chamber, the lower the capacity of the air compressor. Maintaining condensate at minimal levels increases the efficiency of the air compression operation.
Fluid transfer systems utilized in conjunction with air compressors are well known for removing condensate from the air compression chamber. One component of a fluid transfer system is a condensate drain valve. Condensate drain valves enable accumulated condensate to be periodically discharged from the air compression chamber. Although known condensate drain valves are suitable for this purpose, none of the known condensate drain valves efficiently handle the task.
Initially, condensate drain valves were manually operated. Recently, numerous attempts have been made to automate the operation of condensate drain valves. One type of known condensate drain valve utilizes a mechanical float system to trigger the opening of the condensate drain valve. The mechanical float system has a ball positioned in a seat. The ball has a lower density than does the condensate. Consequently, when condensate enters the interior chamber of the valve, the float rises and the condensate escapes through an orifice below the seat. After the condensate escapes, the float returns to its initial position on the seat. Known condensate drain valves that utilize mechanical float systems have numerous disadvantages. Typically, slug and scale alter the surface of the seat. This results in gas leakage when no condensate is present. Energy losses from using such condensate drain valves can range from a few hundred to several thousand dollars per year.
Another known type of condensate drain valve is equipped with a timer. The timer utilizes a power relay which causes an electrically operated condensate drain valve to activate. The timer is set, by a trial and error approach, to periodically open the valve. The condensate is forced out through the valve by the force of the compressed air. The timer keeps the valve open for a fixed amount of time and then causes the valve to close. Because the timer does not precisely correspond to the presence of condensate, the valve will often be open for either too little or too much time. It is estimated that a properly installed timed condensate drain valve loses approximately $1,900 per year. As these valves are often not properly installed, the average valve actually loses much more money.
Another known type of condensate drain valve uses an external vessel to collect condensate formed in the air compression chamber. Sensors, typically reed switches, sense the presence of condensate. When condensate is detected, the sensor causes the valve to open. After the condensate is removed, the sensor causes the valve to close. This type of condensate drain valve is complex and very expensive to manufacture. Frequently, the savings from more efficient air compression are exceeded by the high cost of using this type of condensate drain valve.
Solenoid operated valves are also well known. Solenoid operated valves include an electromagnetic coil assembled over a tube mounted to the body of the valve. An armature is positioned inside the tube and is used to start, stop or divert the flow of liquid or gaseous media. The armature has a spring and a spring loaded sealing disc. In operation, the sealing disc is moved against the force of the spring when the electromagnetic coil is energized thereby opening the valve. Various types of solenoid operated valves using this basic structure are known including: direct acting solenoid valves; pilot operated solenoid valves; and pilot operated with assisted lifting valves.
One known type of solenoid operated condensate drain valve is disclosed in U.S. Pat. No. 4,261,382 to Bridges ("the '382 patent"). The solenoid operated condensate drain valve includes an electrical sensing probe inserted in a condensate drain line upstream of the valve so as to be electrically insulated from the drain line. While electrical isolation is necessary for the solenoid operated condensate drain valve to operate properly, this placement of the probe permits condensate to build-up to unnecessarily high levels thereby reducing the efficiency of the air compressor.
As disclosed in the '382 patent, the electrical sensing probe is connected by electrical leads to an electronic circuit. The electric circuit has voltage supply leads and is connected by electrical leads to the solenoid of the valve. In operation, when the probe does not sense the presence of condensate, the electronic circuit receives the oscillating signal rather than the steady positive output from the probe. When the electric circuit receives the oscillating signal, a timing cycle is initiated during which the solenoid is de-energized and the valve is closed. Although the disclosed electric circuitry performs the intended task, it is overly complex as evidenced by the requirement that the sensor be electrically isolated from the drain line.
The solenoid operated condensate drain valve disclosed in the '382 patent also includes a delay means for providing a desired minimum period between successive operations of the valve such that the valve remains closed for a pre-set period of time.
Because the condensate drain valve does not react to the presence of condensate in the interior chamber of the valve body, excessive condensate necessarily accumulates in the interior chamber of the valve body. Consequently, the efficiency of the air compressor is reduced.
Because of the limitations of known condensate drain valves, a need exists for a valve that can continuously minimize the amount of condensate present in the fluid transfer system of an air compressor.
While there are numerous methods and means for discharging condensate from an air compressor, none are known to be similar to, or to function in the manner of, the present invention.